U.S. patent number 11,228,034 [Application Number 14/961,686] was granted by the patent office on 2022-01-18 for positive active material for rechargeable lithium battery and rechargeable lithium battery.
This patent grant is currently assigned to Samsung SDI Co., Ltd.. The grantee listed for this patent is SAMSUNG SDI CO., LTD.. Invention is credited to Masatsugu Nakano, Yuki Takei.
United States Patent |
11,228,034 |
Takei , et al. |
January 18, 2022 |
Positive active material for rechargeable lithium battery and
rechargeable lithium battery
Abstract
A positive active material for a rechargeable lithium battery
includes a lithium nickel composite oxide having an
I.sub.(003)/I.sub.(104) ratio of greater than or equal to about
0.92 and less than or equal to about 1.02 in X-ray diffraction,
wherein the I.sub.(003)/I.sub.(104) ratio is a ratio of a
diffraction peak intensity I.sub.(003) of a (003) phase and a
diffraction peak intensity I.sub.(104) of a (104) phase. The
lithium nickel composite oxide includes lithium and a
nickel-containing metal, and nickel is present in an amount of
greater than or equal to about 80 atm % based on the total atom
amount of the nickel-containing metal. A rechargeable lithium
battery includes the positive active material.
Inventors: |
Takei; Yuki (Yokohama,
JP), Nakano; Masatsugu (Yokohama, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG SDI CO., LTD. |
Yongin-si |
N/A |
KR |
|
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Assignee: |
Samsung SDI Co., Ltd.
(Yongin-si, KR)
|
Family
ID: |
1000006056480 |
Appl.
No.: |
14/961,686 |
Filed: |
December 7, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20160164094 A1 |
Jun 9, 2016 |
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Foreign Application Priority Data
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Dec 9, 2014 [JP] |
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JP2014-248598 |
Oct 7, 2015 [KR] |
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10-2015-0140980 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M
10/0525 (20130101); C01G 53/42 (20130101); H01M
4/525 (20130101); C01G 53/50 (20130101); H01M
4/505 (20130101); C01P 2002/72 (20130101); H01M
10/052 (20130101); C01P 2004/61 (20130101); C01P
2002/50 (20130101); H01M 4/131 (20130101); C01P
2002/52 (20130101); C01P 2002/74 (20130101) |
Current International
Class: |
H01M
4/525 (20100101); H01M 10/0525 (20100101); H01M
4/505 (20100101); C01G 53/00 (20060101); H01M
10/052 (20100101); H01M 4/131 (20100101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1208249 |
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Jun 2005 |
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CN |
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101030639 |
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Jul 2011 |
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CN |
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1372202 |
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Dec 2003 |
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EP |
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1 372 202 |
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Nov 2013 |
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EP |
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8-22826 |
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Jan 1996 |
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JP |
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08022826 |
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Jan 1996 |
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08022826 |
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Jan 1996 |
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JP |
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10-172564 |
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Jun 1998 |
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10-321224 |
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10321224 |
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10321224 |
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Dec 1998 |
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2000-195514 |
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Jul 2000 |
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JP |
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2000-294240 |
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Oct 2000 |
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JP |
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2009-64702 |
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Mar 2009 |
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JP |
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4320548 |
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Jun 2009 |
|
JP |
|
Other References
CH. Chen, J. Liu, M.E. Stoll, G. Henriksen, D.R. Vissers, K. Amine;
Aluminum-doped lithium nickel cobalt oxide electrodes for
high-power lithium-ion batteries; Journal of Power Sources 128
(2004) 278-285 (Year: 2004). cited by examiner .
Fujita, et al., "LiNi.sub.1-xCo.sub.xO.sub.2 prepared at low
temperature using beta-Ni.sub.1-xCo.sub.x OOH and either LiNO.sub.3
or LiOH,"Journal of Power Sources, vol. 68, 1997, pp. 126-130.
cited by applicant .
EPO Extended Search Report dated Sep. 20, 2016, for corresponding
European Patent Application No. 15198701.3 (15 pages). cited by
applicant .
Abstract and English Machine Translation of Japanese Patent
Publication No. 10-172564 A, Jun. 26, 1998, 13 Pages. cited by
applicant .
Abstract and English Machine Translation of Japanese Patent
Publication No. 2000-195514 A, Jul. 14, 2000, 19 Pages. cited by
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Patent application 15198701.3, (9 pages). cited by applicant .
English machine translation for Japanese Publication 2000-294240
dated Oct. 20, 2000, listed above, (13 pages). cited by applicant
.
Li, D., et al., Synthesis and electrochemical properties of
LiNi.sub.0.85.x Co .sub.x Mn.sub.0.150.sub.2 as cathode materials
for lithium-ion batteries, Journal Of Solid State Electrochemistry,
vol. 12, No. 3, Aug. 11, 2007, pp. 323-327, XP055254058. cited by
applicant .
Song, M., et al., Synthesis of LiNi0.sub.2 cathode by the
combustion method, Journal Of Applied Electrochemistry, vol. 36,
No. 7, May 9, 2006, pp. 801-805, XP019397985. cited by applicant
.
Japanese Office Action dated Aug. 21, 2018, for corresponding
Japanese Patent Application No. 2014-248598 (2 pages). cited by
applicant .
Chinese Notification of the First Office Action dated Aug. 28,
2019, including Search Report dated Aug. 20, 2019, for Patent
Application No. 201510907093.0, 9 pages. cited by applicant .
English Translation of Chinese Notification of the First Office
Action dated Aug. 28, 2019, including Search Report dated Aug. 20,
2019, for Patent Application No. 201510907093.0, 10 pages. cited by
applicant .
Chinese Intellectual Property Office Action dated Jun. 28, 2020,
and accompanying Search Report dated Jun. 17, 2020, with English
Translation for corresponding Chinese Patent Application No.
201510907093.0, 21 pages. cited by applicant .
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accompanying Search Report dated Nov. 20, 2020, with English
Translation, for corresponding Chinese Patent Application No.
201510907093.0, 23 pages. cited by applicant .
The Decision of Final Rejection of the Application in the
Corresponding Chinese Patent Application No. 201510907093.0, with
Machine English Translation, dated Mar. 17, 2021, 18 Pages. cited
by applicant.
|
Primary Examiner: Ruddock; Ula C
Assistant Examiner: Parsons; Thomas H.
Attorney, Agent or Firm: Lewis Roca Rothgerber Christie
LLP
Claims
What is claimed is:
1. A positive active material for a rechargeable lithium battery,
comprising a lithium nickel composite oxide having a
I.sub.(003)/I.sub.(104) ratio of greater than or equal to about
0.92 and less than or equal to about 1.02 in X-ray diffraction,
wherein the I.sub.(003)/I.sub.(104) ratio is a ratio of a
diffraction peak intensity I.sub.(003) of a (003) phase and a
diffraction peak intensity I.sub.(104) of a (104) phase, wherein
the lithium nickel composite oxide comprises lithium and a
nickel-containing metal, wherein the lithium nickel composite oxide
is represented by Chemical Formula 1:
Li.sub.aNi.sub.xCO.sub.yM.sub.zO.sub.2 Chemical Formula 1 wherein,
M is at least one metal selected from aluminum (Al), manganese
(Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg),
titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo),
tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In),
tin (Sn), lanthanum (La), and cerium (Ce), and
0.2.ltoreq.a.ltoreq.1.2, 0.85.ltoreq.x<1, 0<y.ltoreq.0.2,
0.ltoreq.z.ltoreq., and x+y+z=1, wherein a full width at half
maximum FWHM.sub.(003) of a diffraction peak at the (003) phase of
the lithium nickel composite oxide in X-ray diffraction is greater
than or equal to about 0.13 and less than or equal to about 0.15,
wherein the lithium nickel composite oxide has an average
transition metal valence of greater than or equal to about 2.9
calculated from an analysis of an X-ray absorption fine structure
(XAFS) or from a carbon, hydrogen, nitrogen, oxygen (CHNO)
elemental analysis, and wherein the lithium nickel composite oxide
is produced by adding a saturated NaCO.sub.3 aqueous solution to
co-precipitate a carbonate salt of Ni, Co and M to provide a
co-precipitated carbonate salt; mixing lithium hydroxide with the
co-precipitated carbonate salt to provide a mixed powder, and
conducting a single firing at about 750.degree. C. to about
850.degree. C. under an oxygen partial pressure of greater than
about 0.1 MPa and less than about 0.5 MPa to provide the lithium
nickel composite oxide.
2. The positive active material of claim 1, wherein, M is at least
one metal selected from chromium (Cr), iron (Fe), vanadium (V),
magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb),
molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium
(Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce),
0.2.ltoreq.a.ltoreq.1.2, 0.85.ltoreq.x<1, 0<y.ltoreq.0.2,
0.ltoreq.z.ltoreq.0.1, and x+y+z=1.
3. The positive active material of claim 1, wherein an average
particle diameter of secondary particles of the lithium nickel
composite oxide is greater than or equal to about 8 .mu.m and less
than or equal to about 25 .mu.m.
4. The positive active material of claim 1, wherein the lithium
nickel composite oxide is obtained by firing the mixed powder at an
oxygen partial pressure of from 0.2 MPa to less than 0.5 MPa.
5. The positive active material of claim 1, wherein a full width at
half maximum FWHM.sub.(104) of a diffraction peak at the (104)
phase of the lithium nickel composite oxide in X-ray diffraction is
greater than or equal to about 0.15 and less than or equal to about
0.18.
6. A rechargeable lithium battery comprising a positive electrode
comprising the positive active material of claim 1.
7. The rechargeable lithium battery of claim 6, wherein the lithium
nickel composite oxide is represented by Chemical Formula 1:
Li.sub.aNi.sub.xCO.sub.yM.sub.zO.sub.2 Chemical Formula 1 wherein,
M is at least one metal selected from aluminum (Al), manganese
(Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg),
titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo),
tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In),
tin (Sn), lanthanum (La), and cerium (Ce), 0.2.ltoreq.a.ltoreq.1.2,
0.85.ltoreq.x<1, 0<y.ltoreq.0.2, 0.ltoreq.z.ltoreq.0.1, and
x+y+z=1.
8. The rechargeable lithium battery of claim 6, wherein an average
particle diameter of secondary particles of the lithium nickel
composite oxide is greater than or equal to about 8 .mu.m and less
than or equal to about 25 .mu.m.
9. The rechargeable lithium battery of claim 6, wherein the lithium
nickel composite oxide is obtained by firing a lithium nickel
composite oxide precursor at an oxygen partial pressure of greater
than about 0.1 MPa and less than about 0.5 MPa.
10. The rechargeable lithium battery of claim 6, wherein a full
width at half maximum FWHM.sub.(104) of a diffraction peak at the
(104) phase of the lithium nickel composite oxide in X-ray
diffraction is greater than or equal to about 0.15 and less than or
equal to about 0.18.
11. The rechargeable lithium battery of claim 6, wherein the
lithium nickel composite oxide has an average transition metal
valence of greater than or equal to about 2.9 calculated from an
analysis of an X-ray absorption fine structure (XAFS) or from a
carbon, hydrogen, nitrogen, oxygen (CHNO) elemental analysis.
12. The positive active material of claim 1, wherein, M is at least
one metal selected from manganese (Mn), chromium (Cr), iron (Fe),
vanadium (V), titanium (Ti), zirconium (Zr), niobium (Nb),
molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium
(Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce).
Description
CROSS-REFERENCED TO RELATED APPLICATIONS
This application claims priority to and the benefit of Japanese
Patent Application No. 2014-248598, filed in the Japan Patent
Office on Dec. 9, 2014; and Korean Patent Application No.
10-2015-0140980, filed in the Korean Intellectual Property Office
on Oct. 7, 2015, the entire contents of both are incorporated
herein by reference.
BACKGROUND
1. Field
A positive active material for a rechargeable lithium battery and a
rechargeable lithium battery including the same are disclosed.
2. Description of the Related Art
Recently, a lithium nickel composite oxide including nickel has
been suggested as a positive active material capable of realizing a
high potential and high capacity in a rechargeable lithium ion
battery.
However, when the lithium nickel composite oxide includes Ni in a
higher ratio, Ni on the surface thereof is more oxidized (e.g.,
more Ni on the surface thereof is oxidized) as the charge and
discharge cycles are repeated, and forms a rock salt-like structure
(for example, NiO and/or the like) more easily that does not
contribute to the intercalation and deintercalation of Li.
Accordingly, a rechargeable lithium ion battery utilizing this
lithium nickel composite oxide as a positive active material has a
problem of low cycle characteristics.
SUMMARY
An aspect according to one or more embodiments of the present
invention is directed toward a positive active material for a
rechargeable lithium battery suppressed from forming the rock
salt-like structure that does not contribute to the intercalation
and deintercalation of Li, and thereby providing improved cycle
characteristics of the rechargeable lithium battery.
Another aspect according to one or more embodiments of the present
invention is directed toward a rechargeable lithium battery
including the positive active material.
According to one embodiment, a positive active material for a
rechargeable lithium battery includes a lithium nickel composite
oxide having an I.sub.(003)/I.sub.(104) ratio of greater than or
equal to about 0.92 and less than or equal to about 1.02, wherein
the I.sub.(003)/I.sub.(104) ratio is a ratio of a diffraction peak
intensity I.sub.(003) of a (003) phase and a diffraction peak
intensity I.sub.(104) of a (104) phase in X-ray diffraction,
wherein the lithium nickel composite oxide includes lithium and a
nickel-containing metal, and nickel is present in an amount of
greater than or equal to about 80 atm % based on a total atom
amount of the nickel-containing metal.
The lithium nickel composite oxide may be represented by Chemical
Formula 1. Li.sub.aNi.sub.xCo.sub.yM.sub.zO.sub.2 Chemical Formula
1
In Chemical Formula 1, M is at least one metal selected from
aluminum (Al), manganese (Mn), chromium (Cr), iron (Fe), vanadium
(V), magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb),
molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium
(Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce),
0.2.ltoreq.a.ltoreq.1.2, 0.8.ltoreq.x<1, 0<y.ltoreq.0.2,
0.ltoreq.z.ltoreq.0.1, and x+y+z=1.
In Chemical Formula 1, x may be in a range of
0.85.ltoreq.x<1.
An average particle diameter of a secondary particle of the lithium
nickel composite oxide may be greater than or equal to about 8
.mu.m and less than or equal to about 25 .mu.m.
The lithium nickel composite oxide may be obtained by firing a
lithium nickel composite oxide precursor at an oxygen partial
pressure of greater than about 0.1 MPa and less than about 0.5
MPa.
A full width at half maximum FWHM.sub.(003) of a diffraction peak
of the (003) phase of the lithium nickel composite oxide in X-ray
diffraction may be greater than or equal to about 0.13 and less
than or equal to about 0.15.
A full width at half maximum FWHM.sub.(104) of a diffraction peak
of the (104) phase of the lithium nickel composite oxide in X-ray
diffraction may be greater than or equal to about 0.15 and less
than or equal to about 0.18.
The lithium nickel composite oxide may have an average transition
metal valence of greater than or equal to about 2.9 calculated from
an analysis of an X-ray absorption fine structure (XAFS) or a
carbon, hydrogen, nitrogen, oxygen (CHNO) elemental analysis.
According to another embodiment, a rechargeable lithium battery
includes a positive electrode including the positive active
material.
Other embodiments are included in the following detailed
description.
Cycle characteristics of a rechargeable lithium battery may be
improved.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view showing a schematic structure of a
rechargeable lithium battery according to one embodiment.
FIG. 2A is a graph showing the X-ray diffraction analysis of
positive active materials according to Example 1 and Comparative
Example 1.
FIG. 2B is a graph enlarging a region around the diffraction angle
(2.theta.) of 19.degree. in FIG. 2A.
FIG. 3A is a graph showing X-ray diffraction analysis of positive
active materials according to Example 2 and Reference Example
1.
FIG. 3B is a graph enlarging a region around the diffraction angle
(2.theta.) of 19.degree. in FIG. 3A.
FIG. 4A is a graph showing the discharge capacity versus the full
width at half maximum FWHM.sub.(003) of each positive active
material according to Examples 1 to 9, Comparative Examples 1 to 3,
and Reference Examples 1 to 3.
FIG. 4B is a graph showing the cycle characteristics versus the
full width at half maximum FWHM.sub.(003) of each positive active
material according to Examples 1 to 9, Comparative Examples 1 to 3,
and Reference Examples 1 to 3.
FIG. 5A is a graph showing the discharge capacity versus the full
width at half maximum FWHM.sub.(104) of each positive active
material according to Examples 1 to 9, Comparative Examples 1 to 3,
and Reference Examples 1 to 3.
FIG. 5B is a graph showing the cycle characteristics versus the
full width at half maximum FWHM.sub.(104) of each positive active
material according to Examples 1 to 9, Comparative Examples 1 to 3,
and Reference Examples 1 to 3.
FIG. 6 is a graph showing the change in the discharge capacity
depending on the charge and discharge cycles of rechargeable
lithium battery cells according to Example 1 and Comparative
Example 1.
FIG. 7 is a graph showing the change in the discharge capacity
depending on the charge and discharge cycles of rechargeable
lithium battery cells according to Example 2 and Reference Example
1.
FIG. 8 is a graph showing the charge and discharge curves of the
rechargeable lithium battery cells according to Example 1 and
Comparative Example 1 at the 1st cycle.
FIG. 9 is a graph showing the charge and discharge curves of the
rechargeable lithium battery cells according to Example 2 and
Reference Example 1 at the 1st cycle.
FIG. 10 is a graph showing the discharge capacity versus the
discharge rates of the lithium battery cells according to Example 1
and Comparative Example 1.
FIG. 11 is a graph showing the discharge capacity versus the
discharge rates of the lithium battery cells according to Example 2
and Reference Example 1.
DETAILED DESCRIPTION
Hereinafter, embodiments are described in more detail. However,
these embodiments are exemplary, and this disclosure is not limited
thereto. Expressions such as "at least one of" or "at least one
selected from" when preceding a list of elements, modify the entire
list of elements and do not modify the individual elements of the
list. Further, the use of "may" when describing embodiments of the
present invention refers to "one or more embodiments of the present
invention." Also, the term "exemplary" is intended to refer to an
example or illustration. It will be understood that when an element
or layer is referred to as being "on", "connected to", "coupled
to", or "adjacent to" another element or layer, it can be directly
on, connected to, coupled to, or adjacent to the other element or
layer, or one or more intervening elements or layers may be
present. In contrast, when an element or layer is referred to as
being "directly on," "directly connected to", "directly coupled
to", or "immediately adjacent to" another element or layer, there
are no intervening elements or layers present. As used herein, the
term "substantially," "about," and similar terms are used as terms
of approximation and not as terms of degree, and are intended to
account for the inherent deviations in measured or calculated
values that would be recognized by those of ordinary skill in the
art. Also, any numerical range recited herein is intended to
include all sub-ranges of the same numerical precision subsumed
within the recited range. For example, a range of "1.0 to 10.0" is
intended to include all subranges between (and including) the
recited minimum value of 1.0 and the recited maximum value of 10.0,
that is, having a minimum value equal to or greater than 1.0 and a
maximum value equal to or less than 10.0, such as, for example, 2.4
to 7.6. Any maximum numerical limitation recited herein is intended
to include all lower numerical limitations subsumed therein and any
minimum numerical limitation recited in this specification is
intended to include all higher numerical limitations subsumed
therein. Accordingly, Applicant reserves the right to amend this
specification, including the claims, to expressly recite any
sub-range subsumed within the ranges expressly recited herein. All
such ranges are intended to be inherently described in this
specification such that amending to expressly recite any such
subranges would comply with the requirements of 35 U.S.C. .sctn.
112, first paragraph, or 35 U.S.C. .sctn. 112(a), and 35 U.S.C.
.sctn. 132(a).
Hereinafter, a rechargeable lithium battery according to one
embodiment is described referring to FIG. 1.
FIG. 1 is a cross-sectional view showing a schematic structure of a
rechargeable lithium battery according to one embodiment.
Referring to FIG. 1, a rechargeable lithium battery 10 includes a
positive electrode 20, a negative electrode 30, and a separator
layer 40. The rechargeable lithium ion battery 10 is not
particularly limited in shape, and may have any suitable shape such
as a cylinder, a prism, a laminate shape, a button shape, and/or
the like.
The positive electrode 20 includes a current collector 21 and a
positive active material layer 22 formed on the current collector
21.
The current collector 21 may be any suitable conductor, for
example, aluminum (Al), stainless steel, nickel-plated steel,
and/or the like.
The positive active material layer 22 includes a positive active
material, and may further include at least one selected from a
conductive material and a binder.
Contents of the positive active material, the conductive material,
and the binder are not particularly limited, and may be any
suitable content applicable to a general rechargeable lithium
battery.
Hereinafter, the positive active material is described.
The positive active material may include a lithium nickel composite
oxide.
The lithium nickel composite oxide has the following parameters
within respective set or predetermined ranges: an
I.sub.(003)/I.sub.(104) ratio between a diffraction peak intensity
I.sub.(003) of a (003) phase and a diffraction peak intensity
I.sub.(104) of a (104) phase in X-ray diffraction; a full width at
half maximum FWHM.sub.(003) of a diffraction peak of a (003) phase;
a full width of half maximum FWHM.sub.(104) of a diffraction peak
of a (104) phase; and an average valence of the transition metal.
The lithium nickel composite oxide improves the cycle
characteristics of a rechargeable lithium battery.
For example, the I.sub.(003)/I.sub.(104) ratio between a
diffraction peak intensity I.sub.(003) of a (003) phase and a
diffraction peak intensity I.sub.(104) of a (104) phase in X-ray
diffraction may be greater than or equal to about 0.92 and less
than or equal to about 1.02, for example, greater than or equal to
about 0.93 and less than or equal to about 1.01. When the
I.sub.(003)/I.sub.(104) ratio between the diffraction peak
intensities of the (003) phase and the (104) phases falls within
these ranges, the discharge capacity of a rechargeable lithium
battery increases and cycle characteristics are improved.
The full width at half maximum FWHM.sub.(003) of a diffraction peak
of a (003) phase in X-ray diffraction may be greater than or equal
to about 0.13 and less than or equal to about 0.15, for example,
greater than or equal to about 0.130 and less than or equal to
about 1.145. When the full width at half maximum FWHM.sub.(003) of
a diffraction peak of a (003) phase is within these ranges,
discharge capacity of a rechargeable lithium battery increases and
cycle characteristics may be improved.
The full width at half maximum FWHM.sub.(104) of a diffraction peak
of a (104) phase in X-ray diffraction may be greater than or equal
to about 0.15 and less than or equal to about 0.18, for example,
greater than or equal to about 0.152 and less than or equal to
about 0.178. When the full width at half maximum FWHM.sub.(104) of
a diffraction peak of a (104) phase is within these ranges,
discharge capacity of a rechargeable lithium battery increases and
cycle characteristics may be improved.
The diffraction peak intensity ratio I.sub.(003)/I.sub.(104), the
full width at half maximum FWHM.sub.(003) of a diffraction peak of
a (003) phase and the full width at half maximum FWHM.sub.(104) of
a diffraction peak of a (104) phase may be, for example, obtained
from an X-ray diffraction pattern of a lithium nickel composite
oxide.
The X-ray diffraction pattern of the lithium nickel composite oxide
may be, for example, obtained by a known X-ray diffraction
measurement method.
The lithium nickel composite oxide may be represented as
LiMeO.sub.2 (Me represents transition metals including nickel). An
average valence of the transition metals of the lithium nickel
composite oxide (e.g., an average valence of Me when all transition
metals are represented as a single transition metal Me despite the
number of transition metals included in the lithium nickel
composite) according to one embodiment may be greater than or equal
to about 2.9 (for example, greater than or equal to about 2.90),
and less than or equal to about 3. When the average valence of the
transition metals falls within the above described range, cycle
characteristics of a rechargeable lithium battery may be
improved.
The average valence of the transition metals of the lithium nickel
composite oxide may be, for example, calculated from the oxygen
content by a carbon, hydrogen, nitrogen, oxygen (CHNO) inorganic
elemental analysis for a lithium nickel composite oxide.
For example, the number of moles of each metal element (the lithium
element and the transition metal element including nickel) included
in the lithium nickel composite oxide is obtained through ICP
(Inductively Coupled Plasma) elemental analysis and/or the like. As
twice the obtained total number of moles of transition metal
elements (e.g., nickel and any other transition metals included in
the lithium nickel composite oxide, excluding lithium) is the
theoretical number of moles of oxygen, when it is corresponded to
the moles of oxygen (e.g., when the moles of oxygen is obtained by
doubling the total number of moles of the transition metal
elements), the composition formula of the lithium nickel composite
oxide may be obtained by utilizing the number of moles of lithium,
transition metals, and oxygen. An oxygen content (e.g., a weight
percentage of oxygen in the lithium nickel composite oxide) may be
obtained from the composition formula (e.g., by calculating the
weight of each of Li, nickel, oxygen and any other transition
metals in one mole of the lithium nickel composite oxide) and is
regarded as (represented by) A wt %. In other words, the A wt % is
the theoretical value of the oxygen content (e.g., the theoretical
weight percentage of oxygen in one mole of the lithium nickel
composite oxide based on the total weight of the lithium nickel
composite oxide).
Subsequently, the oxygen content obtained through a CHNO inorganic
elemental analysis is regarded as (represented by) B wt %. In other
words, the B wt % is an actual value of the oxygen content.
Herein, since the lithium nickel composite oxide is represented as
LiMeO.sub.2 (Me is a transition metal), the average valence of
transition metals (represented by Me) has a theoretical value of
+3, when lithium (Li) is regarded to have a valence of +1, while
oxygen (O) is regarded to have a valence of -2. As the ratio
between the amount the oxygen and the amount of the transition
metals is substantially constant, the actual value of the average
valence of transition metals included in the lithium nickel
composite oxide may be obtained by multiplying a ratio of the
theoretical value A wt % and the actual value B wt % of the oxygen
content by the theoretical value 3 of the average valence of
transition metals.
In other words, the actual value of the average valence of
transition metals may be calculated through the following Equation
1. Average valence of transition metal=[B(wt %)/A(wt %)].times.3
Equation 1
In addition, the average valence of transition metals included in
the lithium nickel composite oxide may be calculated, for example,
through an X-ray absorption fine structure (XAFS).
The lithium nickel composite oxide according to one embodiment may
be manufactured by firing (heat-treating) a lithium nickel
composite oxide precursor under an oxygen partial pressure ranging
from greater than about 0.1 MPa to less than about 0.5 MPa.
When the lithium nickel composite oxide precursor is fired
(heat-treated) within the above described oxygen partial pressure
range, the lithium nickel composite oxide may be suppressed from
having crystal growth (e.g., suppressed from having excessive
crystal growth). Accordingly, the lithium nickel composite oxide
may be manufactured under a high lithium and temperature (e.g.,
high temperature) condition in which a crystal easily grows.
This high lithium and temperature (e.g., high temperature)
condition in the related art makes it excessively easily for a
crystal to grow and thus deteriorates the characteristics of a
rechargeable lithium battery due to rapid crystal growth or
excessively high crystallinity.
Herein, the high lithium condition refers to, for example, a
condition in which Li has a mole ratio of 1 or more relative to the
transition metal elements except for Li in the lithium nickel
composite oxide precursor. In addition, the high temperature
condition refers to, for example, a condition in which the lithium
nickel composite oxide precursor is fired at a temperature ranging
from greater than or equal to about 750.degree. C. to less than or
equal to about 850.degree. C.
In the lithium nickel composite oxide according to one embodiment,
the firing of its precursor under a high oxygen partial pressure
and under a high lithium and temperature condition may control the
crystal growing speed of the lithium nickel composite oxide and
promote solid dissolution of Li with other elements (such as nickel
and/or the like except for Li). Accordingly, stability of the
lithium nickel composite oxide may be much improved.
In addition, the lithium nickel composite oxide according to one
embodiment reacts with moisture or carbon dioxide in the air and
generates impurities (such as Li.sub.2CO.sub.3 and/or the like),
and thus may consume LiOH that primarily deteriorates the discharge
capacity through the firing under the high temperature condition.
Accordingly, stability of the lithium nickel composite oxide may be
improved.
The lithium nickel composite oxide of one embodiment having high
stability may be suppressed from the formation of the rock
salt-like structure (that does not contributing to the
intercalation and deintercalation of Li) during the repeated charge
and discharge cycles. Accordingly, the lithium nickel composite
oxide of one embodiment as a positive active material may improve
the characteristics of a rechargeable lithium battery.
In other words, the lithium nickel composite oxide according to one
embodiment may be manufactured by firing its precursor(s) under a
high oxygen partial pressure ranging from about 0.1 MPa to less
than about 0.5 MPa. Accordingly, the average valence of the
transition metals included in the lithium nickel composite oxide
may be increased to greater than or equal to about 2.9. In
addition, the lithium nickel composite oxide is suppressed from
excessive crystal growth under the firing condition and thus may
have a lower diffraction peak intensity ratio
I.sub.(003)/I.sub.(104) (as a crystalline height index) within a
range of greater than or equal to about 0.92 to less than or equal
to about 1.02. Furthermore, as the crystal growth is suppressed
under the firing condition, a full width at half maximum, that is,
FWHM.sub.(003) of the diffraction peak of the (003) phase becomes
widened to greater than or equal to about 0.13 to less than or
equal to about 0.15, while FWHM.sub.(104) of the diffraction peak
of the (104) phase becomes widened to greater than or equal to
about 0.15 to less than or equal to about 0.18. Hereinafter, one of
more of these ranges are referred to as "the range(s) of one
embodiment."
The lithium nickel composite oxide includes a nickel-containing
metal and lithium, and nickel is present in an amount of greater
than or equal to about 80 atm % based on the total atom amount of
the nickel-containing metal (e.g., the nickel-containing metal may
include 100 atm % nickel, or may include nickel and at least one
metal excluding lithium and nickel). In other words, the lithium
nickel composite oxide may be a high nickel-based composite
oxide.
The lithium nickel composite oxide may be represented by Chemical
Formula 1. Li.sub.aNi.sub.xCo.sub.yM.sub.zO.sub.2 Chemical Formula
1
In Chemical Formula 1, M is at least one metal selected from
aluminum (Al), manganese (Mn), chromium (Cr), iron (Fe), vanadium
(V), magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb),
molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium
(Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce),
0.2.ltoreq.a.ltoreq.1.2, 0.8.ltoreq.x<1, 0<y.ltoreq.00.2,
0.ltoreq.z.ltoreq.0.1, and x+y+z=1.
For example, in Chemical Formula 1, x may be in a range of
0.85.ltoreq.x<1.
According to one embodiment, a lithium nickel composite oxide
having a high Ni ratio as shown in Chemical Formula 1 may be more
effectively suppressed from the generation of a rock salt-like
structure not contributing to the intercalation and deintercalation
of Li.
A lithium nickel composite oxide according to one embodiment
includes secondary particles where fine primary particles are
agglomerated, and an average particle diameter (D50) of the
secondary particles may be greater than or equal to about 8 .mu.m
and less than or equal to about 25 .mu.m, for example, greater than
or equal to about 8 .mu.m and less than or equal to about 20 .mu.m.
When the secondary particles of the lithium nickel composite oxide
have an average particle diameter within these ranges,
characteristics of a rechargeable lithium battery may be more
effectively improved.
Herein, D50 indicates a particle diameter where an accumulated
value is 50% in a particle diameter distribution curve and is
called a median diameter. The particle diameter distribution for
calculating the average particle diameter (D50) of the secondary
particles may be obtained utilizing a known method, for example, a
laser diffraction scattering method. In addition, the average
particle diameter of the secondary particles indicates a diameter
when the secondary particle is considered to be spherical.
Hereinafter, a method of manufacturing the lithium nickel composite
oxide is described. The method of manufacturing the lithium
nickel-based oxide particle is not particularly limited, but may
be, for example, a co-precipitation method.
Hereinafter, the method of manufacturing the lithium nickel-based
oxide particle utilizing the co-precipitation method is
illustrated, but is only one example, and the mixing amounts, raw
materials, and/or the like are not limited thereto.
First, nickel sulfate.6 hydrate (NiSO.sub.4.6H.sub.2O), cobalt
sulfate.5 hydrate (CoSO.sub.4.5H.sub.2O), and a metal
(M)-containing compound are dissolved in ion exchange water,
thereby preparing a mixed aqueous solution. Herein, the nickel
sulfate.6 hydrate, the cobalt sulfate.5 hydrate, and the metal
(M)-containing compound may be utilized, for example, in a total
weight of about 20 wt %, based on the entire (total) weight of the
mixed aqueous solution. In addition, the nickel sulfate.6 hydrate,
the cobalt sulfate.5 hydrate, and the metal (M)-containing compound
may be mixed in a desired mole ratio among Ni, Co, and M. On the
other hand, the mole ratio of each element may be determined
depending on the composition of the prepared lithium nickel-based
oxide, for example,
Li.sub.1.06Ni.sub.0.9Co.sub.0.08Mn.sub.0.02O.sub.2 may be prepared
in a mole ratio of 90:8:2=Ni:Co:Mn.
In the metal (M)-containing compound, the metal element, M, may be
at least one selected from aluminum (Al), manganese (Mn), chromium
(Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti),
zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper
(Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum
(La), and cerium (Ce). Examples of the metal (M)-containing
compound may be various suitable salts (such as sulfates and
nitrates of the metal element, M), oxides, hydroxides, and/or the
like.
In addition, a set or predetermined amount, for example, about 500
ml, of ion exchange water is added to the mixed aqueous solution
which refers to an aqueous solution of a reaction layer, and the
mixture is maintained at about 50.degree. C. Hereinafter, the
aqueous solution of the reaction layer is called a reaction layer
aqueous solution. Subsequently, the ion exchange water is bubbled
by an inert gas such as nitrogen and/or the like to remove oxygen
dissolved therein. Then, the aforementioned mixed aqueous solution
is added thereto, while the reaction layer aqueous solution is
agitated and maintained at 50.degree. C. The addition speed is not
particularly limited, but if excessively fast, a uniform precursor
(co-precipitated carbonate salt) may not be obtained. For example,
the addition speed may be about 3 ml/min.
Then, a saturated NaCO.sub.3 aqueous solution is added in an excess
amount regarding (relative to the amount of) the Ni, Co, and M of
the mixed aqueous solution to the reaction layer aqueous solution.
The reaction layer aqueous solution is maintained at a pH of 11.5
and a temperature of 50.degree. C. during the addition. The
addition may be performed, for example, at a set or predetermined
agitation speed for a set or predetermined time. Accordingly, a
carbonate salt of each metal element is co-precipitated.
Continuously, the co-precipitated carbonate salt is taken from the
reaction layer aqueous solution through solid-liquid separation,
for example, adsorption-filtering, and then rinsed (e.g., cleaned)
with ion exchange water. Subsequently, the co-precipitated
carbonate salt is vacuum-dried, for example, at about 100.degree.
C. for about 10 hours (h).
Subsequently, the dried co-precipitated carbonate salt is ground
with a mortar and pestle for several minutes to obtain a dry
powder, and the dry powder is mixed with lithium hydroxide (LiOH)
to obtain a mixed powder. Herein, a mole ratio of Li with Ni, Co,
and M (Ni+Co+M=Me) is determined by the composition of the lithium
nickel composite oxide. For example,
Li.sub.1.06Ni.sub.0.9Co.sub.0.08Mn.sub.0.02O.sub.2 may be prepared
in a Li/Me mole ratio of about 1.06 between Li and Me.
The mixed powder is fired at a set or predetermined temperature
under a high oxygen partial pressure for a set or predetermined
time. Accordingly, lithium nickel composite oxide according to one
embodiment is obtained.
During the firing, the oxygen partial pressure may be in a range of
greater than about 0.1 MPa and less than about 0.5 MPa, for
example, greater than about 0.1 MPa and less than about 0.4 MPa. In
addition, the firing time may be, for example, about 10 hours, and
the firing temperature may be, for example, in a range of about
750.degree. C. to about 850.degree. C.
The lithium nickel composite oxide prepared in the above method
according to one embodiment may have a diffraction peak intensity
ratio I.sub.(003)/I.sub.(104) of the (003) phase and the (104)
phase, a full width at half maximum FWHM.sub.(003) of diffraction
peak of the (003) phase, a full width at half maximum
FWHM.sub.(104) of diffraction peak of the (104) phase, and the
average valence of transition metals within the above described
ranges.
On the other hand, each parameter of the lithium nickel composite
oxide may be adjusted by adjusting an agitation speed and agitation
time during the addition, a Li/Me mole ratio between Li and Me, an
oxygen partial pressure, firing time and firing temperature during
the firing, and/or the like.
For example, as the firing temperature is higher, a diffraction
peak intensity ratio I.sub.(003)/I.sub.(104) of the (003) phase and
the (104) phase tends to be higher, while the full width at half
maximum FWHM.sub.(003) and FWHM.sub.(104) of the diffraction peaks
of the (003) phase and the (104) phase tend to be smaller.
In addition, as the mole ratio Li/Me is higher, the diffraction
peak intensity ratio I.sub.(003)/I.sub.(104) of the (003) phase and
the (104) phase tends to be higher, while the full width at half
maximum FWHM.sub.(003) and FWHM.sub.(104) of the diffraction peaks
of the (003) phase and the (104) phase tend to be smaller.
In addition, as the oxygen partial pressure during the firing is
higher, the average valence of transition metals included in the
lithium nickel composite oxide tends to be higher, while the full
width at half maximum FWHM.sub.(104) of the diffraction peak of the
(104) phase tends to be larger.
Through the above processes, the lithium nickel composite oxide may
be prepared.
A positive active material layer according to one embodiment may
include other positive active materials in addition to the lithium
nickel composite oxide.
The conductive material is not particularly limited as long as it
increases conductivity of a positive electrode, and may be, for
example, carbon black (such as ketjen black, acetylene black,
and/or the like), natural graphite, artificial graphite, carbon
nanotubes, graphene, fiber-shaped carbon (such as carbon nanofibers
and/or the like), and/or a composite of the fiber-shaped carbon and
carbon black.
The binder may be, for example, polyvinylidene fluoride, an
ethylene-propylene-diene terpolymer, a styrene-butadiene rubber, an
acrylonitrile-butadiene rubber, a fluorine rubber,
polyvinylacetate, polymethylmethacrylate, polyethylene,
nitrocellulose, and/or the like, and is not particularly limited as
long as it binds the positive active material and the conductive
material on a current collector, and simultaneously (or
concurrently) has oxidation resistance for high potential of a
positive electrode and electrolyte stability.
The positive electrode 20 may be manufactured in the following
method. First, the positive active material, the conductive
material, and the binder are mixed in a desirable ratio and
dispersed in an organic solvent (such as N-methyl-2-pyrrolidone) to
form a slurry. Subsequently, the slurry is coated on a current
collector 21 and then dried to form a positive active material
layer 22. Herein, the coating method is not particularly limited,
and may be, for example, a knife coating method, a gravure coating
method, and/or the like. Then, the positive active material layer
22 is compressed utilizing a compressor to a desirable thickness to
manufacture a positive electrode 20. A thickness of the positive
active material layer 22 is not particularly limited, and may be
any suitable thickness that is applicable to a positive active
material layer of a rechargeable lithium battery.
The negative electrode 30 includes a current collector 31 and a
negative active material layer 32 formed on the current collector
31.
The current collector 31 may be any suitable conductor, for
example, copper, a copper alloy, aluminum, stainless steel,
nickel-plated steel, and/or the like.
The negative active material layer 32 may be any suitable negative
active material layer of a rechargeable lithium battery. For
example, the negative active material layer 32 may include a
negative active material, and may further include a binder.
The negative active material may include a carbon-based material, a
silicon-based material, a tin-based material, a lithium metal
oxide, a metal lithium, and/or the like, which may be utilized
singularly or as a mixture of two or more. The carbon-based
material may be, for example, a graphite-based material such as
artificial graphite, natural graphite, a mixture of artificial
graphite and natural graphite, natural graphite coated with
artificial graphite, and/or the like. The silicon-based material
may be, for example, silicon, a silicon oxide, a silicon-containing
alloy, a mixture of the graphite-based material with the foregoing
materials, and/or the like. The silicon oxide may be represented by
SiO.sub.x (0<x.ltoreq.2). The silicon-containing alloy may be an
alloy including silicon in the largest amount of the total metal
elements (e.g., silicon being the metal element that is present in
the largest amount of all the metal elements) based on the total
amount of the alloy, for example, a Si--Al--Fe alloy. The tin-based
material may be, for example, tin, a tin oxide, a tin-containing
alloy, a mixture of the graphite-based material with the foregoing
materials, and/or the like. The lithium metal oxide may be, for
example, a titanium oxide compound such as
Li.sub.4Ti.sub.5O.sub.12. According to one embodiment, among them,
graphite may further improve cycle-life characteristics of a
rechargeable lithium battery.
The binder is not particularly limited, and may be the same binder
as the binder of the positive electrode.
A weight ratio of the negative active material and the binder is
not particularly limited, and may be a weight ratio of a related
art rechargeable lithium battery.
The negative electrode 30 may be manufactured as follows. The
negative active material and the binder are mixed in a desired
ratio and the mixture is dispersed in an appropriate solvent (such
as water and/or the like) to prepare a slurry. Then, the slurry is
applied on a current collector 31 and dried to form a negative
active material layer 32. Then, the negative active material layer
32 is compressed to have a desired thickness by utilizing a
compressor, thereby manufacturing the negative electrode 30.
Herein, the negative active material layer 32 has no particularly
limited thickness, but may have any suitable thickness that a
negative active material layer for a rechargeable lithium ion
battery may have. In addition, when metal lithium is utilized as
the negative active material layer 32, the metal lithium may be
overlapped with (e.g., laminated or coated on) the current
collector 31.
The separator layer 40 may include a separator and an
electrolyte.
The separator is not particularly limited, and may be any suitable
separator utilized for a rechargeable lithium ion battery. For
example, a porous layer or a non-woven fabric showing excellent
high rate discharge performance and/or the like may be utilized
alone or as a mixture (e.g., in a laminated structure).
A substrate of the separator may include, for example, a
polyolefin-based resin, a polyester-based resin, polyvinylidene
difluoride (PVDF), a vinylidene difluoride-hexafluoropropylene
copolymer, a vinylidene difluoride-perfluorovinylether copolymer, a
vinylidene difluoride-tetrafluoroethylene copolymer, a vinylidene
difluoride-trifluoroethylene copolymer, a vinylidene
difluoride-fluoroethylene copolymer, a vinylidene
difluoride-hexafluoroacetone copolymer, a vinylidene
difluoride-ethylene copolymer, a vinylidene difluoride-propylene
copolymer, a vinylidene difluoride-trifluoropropylene copolymer, a
vinylidene difluoride-tetrafluoroethylene-hexafluoropropylene
copolymer, a vinylidene difluoride-ethylene-tetrafluoroethylene
copolymer, and/or the like. The polyolefin-based resin may be
polyethylene, polypropylene, and/or the like; and the
polyester-based resin may be polyethylene terephthalate,
polybutylene terephthalate, and/or the like.
A porosity of the separator is not particularly limited, and may be
any suitable porosity that a separator of a rechargeable lithium
battery may have.
The separator may be formed on at least one side of the substrate,
and may include a coating layer including an inorganic filler. The
inorganic filler may include Al.sub.2O.sub.3, Mg(OH).sub.2,
SiO.sub.2, and/or the like. The coating layer including the
inorganic filler may inhibit direct contact between the positive
electrode and the separator, inhibit oxidation and decomposition of
an electrolyte on the surface of the positive electrode during
storage at a high temperature, and suppress the generation of gas
which is a decomposed product of the electrolyte.
The electrolyte may include an electrolyte salt in a non-aqueous
solvent.
The non-aqueous solvent may be, for example, cyclic carbonates
(such as propylene carbonate, ethylene carbonate, butylene
carbonate, chloroethylene carbonate, vinylene carbonate, and/or the
like); linear carbonates (such as dimethyl carbonate, diethyl
carbonate, ethylmethyl carbonate, and/or the like); cyclic esters
(such as .gamma.-butyrolactone, .gamma.-valerolactone, and/or the
like); linear esters (such as methyl formate, methyl acetate,
butyric acid methyl, and/or the like); tetrahydrofuran or a
derivative thereof; ethers (such as 1,3-dioxane, 1,4-dioxane,
1,2-dimethoxy ethane, 1,4-dibutoxyethane, methyl diglyme, and/or
the like); nitriles (such as acetonitrile, benzonitrile, and/or the
like); dioxolane or a derivative thereof; ethylene sulfide;
sulfolane; and/or sultone or a derivative thereof, which may be
utilized singularly or as a mixture of two or more, without being
limited thereto.
The electrolytic salt may be, for example, an inorganic ion salt
including lithium (Li), sodium (Na), and/or potassium (K), such as
LiClO.sub.4, LiBF.sub.4, LiAsF.sub.6, LiPF.sub.6,
LiPF.sub.6-x(CnF.sub.2n+1).sub.x (1<x<6, n=1 or 2), LiSCN,
LiBr, LiI, Li.sub.2SO.sub.4, Li.sub.2B.sub.10Cl.sub.10,
NaClO.sub.4, NaI, NaSCN, NaBr, KClO.sub.4, KSCN, and/or the like;
and/or an organic ion salt such as LiCF.sub.3SO.sub.3,
LiN(CF.sub.3SO.sub.2).sub.2, LiN(C.sub.2F.sub.5SO.sub.2).sub.2,
LiN(CF.sub.3SO.sub.2)(C.sub.4F.sub.9SO.sub.2),
LiC(CF.sub.3SO.sub.2).sub.3, LiC(C.sub.2F.sub.5SO.sub.2).sub.3,
(CH.sub.3).sub.4NBF.sub.4, (CH.sub.3).sub.4NBr,
(C.sub.2H.sub.5).sub.4NClO.sub.4, (C.sub.2H.sub.5).sub.4NI,
(C.sub.3H.sub.7).sub.4NBr, (n-C.sub.4H.sub.9).sub.4NClO.sub.4,
(n-C.sub.4H.sub.9).sub.4NI, (C.sub.2H.sub.5).sub.4N-maleate,
(C.sub.2H.sub.5).sub.4N-benzoate, (C.sub.2H.sub.5).sub.4N-phtalate,
lithium stearyl sulfonate, lithium octyl sulfonate, lithium
dodecylbenzene sulfonate, and/or the like. The ionic compounds may
be utilized singularly or in a mixture of two or more.
A concentration of the electrolyte salt is not particularly
limited, and may be, for example, about 0.5 mol/L to about 2.0
mol/L.
The electrolyte may further include various suitable additives such
as a negative electrode SEI (Solid Electrolyte Interface) forming
agent, a surfactant, and/or the like.
Such additives may be, for example, succinic anhydride, lithium
bis(oxalato)borate, lithium tetrafluoroborate, a dinitrile
compound, propane sultone, butane sultone, propene sultone,
3-sulfolene, a fluorinated allylether, a fluorinated acrylate,
and/or the like.
The concentration of the additives may be any suitable one that is
utilized in a general rechargeable lithium ion battery.
Hereinafter, a method of manufacturing a rechargeable lithium ion
battery 10 is described.
The separator is disposed between the positive electrode 20 and the
negative electrode 30 to manufacture an electrode structure, and
the electrode structure is processed to have a desired shape, for
example, a cylinder, a prism, a laminate shape, a button shape,
and/or the like, and inserted into a container having the same
shape. Then, the non-aqueous electrolyte is injected into the
container, and the electrolyte is impregnated in the pores in the
separator, thereby manufacturing a rechargeable lithium
battery.
Hereinafter, the embodiments are illustrated in more detail with
reference to the following examples. However, these examples are
exemplary, and the present disclosure is not limited thereto.
Furthermore, what is not described in this disclosure may be
sufficiently understood by those who have knowledge in this field
and will not be illustrated herein.
Preparation of Lithium Nickel Composite Oxide
Examples 1 to 9, Comparative Examples 1 to 3, and Reference
Examples 1 to 3
Nickel sulfate.6 hydrate (NiSO.sub.4.6H.sub.2O), cobalt sulfate.5
hydrate (CoSO.sub.4.5H.sub.2O), and manganese sulfate.7 hydrate
(MnSO.sub.4.7H.sub.2O) (or aluminum nitrate (Al(NO.sub.3).sub.3))
were dissolved in ion exchange water, thus preparing a mixed
aqueous solution. Herein, the nickel sulfate.6 hydrate, the cobalt
sulfate.5 hydrate, and the manganese sulfate.7 hydrate (or aluminum
nitrate) were utilized in a total weight of 20 wt % based on the
entire weight of the mixed aqueous solution. In addition, the
nickel sulfate.6 hydrate, the cobalt sulfate.5 hydrate, and the
manganese sulfate.7 hydrate (or aluminum nitrate) were mixed in a
mole ratio of 90:8:2 or 85:12:3 among Ni, Co, and Mn (or Al).
In addition, 500 ml of ion exchange water was injected into the
reaction layer, and the mixture was maintained at 50.degree. C.
Subsequently, the ion exchange water was bubbled by nitrogen gas,
thereby removing oxygen dissolved therein. Subsequently, the
reaction layer aqueous solution was agitated and maintained at
50.degree. C., and the above mixed aqueous solution was added
thereto in a dropwise fashion at a speed of 3 ml/min. Then, a
NaCO.sub.3 aqueous solution excessively saturated regarding Ni and
Co in the mixed aqueous solution was added (e.g., more NaCO.sub.3
than what is needed to saturate Ni and Co was added) to a reaction
bath aqueous solution in a dropwise fashion. The reaction layer
aqueous solution was maintained at a pH of 11.5 and a temperature
of 50.degree. C. during the addition. Herein, the agitation was
performed at a circumferential speed of 4 to 5 m/s for 10 hours.
Accordingly, a carbonate salt of each metal element was
co-precipitated.
Subsequently, the co-precipitated carbonate salt was taken from the
reaction layer aqueous solution through solid-liquid separation,
for example, adsorption filtering, and then cleaned (e.g., rinsed)
with ion exchange water. Subsequently, the co-precipitated
carbonate salt was vacuum-dried, for example, at about 100.degree.
C. for about 10 hours (h).
Then, the dried co-precipitated carbonate salt was ground with a
mortar and pestle for several minutes to obtain a dry powder, and
the dry powder was mixed with lithium hydroxide (LiOH) to obtain a
mixed powder. Herein, Li and Me (Ni+Co+Mn (or Al)) were mixed in a
Li/Me mole ratio of 1.06 or 1.0.
Subsequently, the mixed powder was fired at a temperature of
770.degree. C. or 790.degree. C. under an oxygen partial pressure
of 0.1 MPa, 0.2 Mpa, or 0.5 Mpa for 10 hours, thereby manufacturing
a lithium nickel composite oxide.
The composition of each lithium nickel composite oxide according to
Examples 1 to 9, Comparative Examples 1 to 3, and Reference
Examples 1 to 3 and its firing condition are provided in Table
1.
TABLE-US-00001 TABLE 1 Composition Chemical Firing Oxygen partial
Formula temperature pressure Example 1
Li.sub.1.06Ni.sub.0.9Co.sub.0.08Mn.sub.0.02O.sub.2 770.degree. C.
0.2 MPa Example 2
Li.sub.1.03Ni.sub.0.9Co.sub.0.08Mn.sub.0.02O.sub.2 770.degree. C.
0.2 MPa Example 3
Li.sub.1.03Ni.sub.0.9Co.sub.0.08Mn.sub.0.02O.sub.2 790.degree. C.
0.2 MPa Example 4 LiNi.sub.0.9Co.sub.0.08Al.sub.0.02O.sub.2
770.degree. C. 0.2 MPa Example 5
LiNi.sub.0.9Co.sub.0.08Al.sub.0.02O.sub.2 790.degree. C. 0.2 MPa
Example 6 LiNi.sub.0.85Co.sub.0.12Mn.sub.0.03O.sub.2 770.degree. C.
0.2 MPa Example 7 LiNi.sub.0.85Co.sub.0.12Mn.sub.0.03O.sub.2
790.degree. C. 0.2 MPa Example 8
LiNi.sub.0.85Co.sub.0.12Al.sub.0.03O.sub.2 770.degree. C. 0.2 MPa
Example 9 LiNi.sub.0.85Co.sub.0.12Al.sub.0.03O.sub.2 790.degree. C.
0.2 MPa Comparative
Li.sub.1.06Ni.sub.0.9Co.sub.0.08Mn.sub.0.02O.sub.2 770.degree. C.
0.1 MPa Example 1 Reference
Li.sub.1.03Ni.sub.0.9Co.sub.0.08Mn.sub.0.02O.sub.2 770.degree. C.
0.1 MPa Example 1 Reference
LiNi.sub.0.9Co.sub.0.08Mn.sub.0.02O.sub.2 770.degree. C. 0.5 MPa
Example 2 Reference LiNi.sub.0.85Co.sub.0.12Mn.sub.0.03O.sub.2
770.degree. C. 0.5 MPa Example 3 Comparative
LiNi.sub.0.85Co.sub.0.12Al.sub.0.03O.sub.2 770.degree. C. 0.5 MPa
Example 2 Comparative LiNi.sub.0.85Co.sub.0.12Al.sub.0.03O.sub.2
790.degree. C. 0.5 MPa Example 3
Evaluation 1: X-ray Diffraction
X-ray diffraction of each lithium nickel composite oxide according
to Examples 1 to 9, Comparative Examples 1 to 3, and Reference
Examples 1 to 3 was measured.
For example, FIGS. 2A and 2B show X-ray diffraction results of
Example 1 and Comparative Example 1, and FIGS. 3A and 3B show X-ray
diffraction results of Example 2 and Reference Example 1.
FIG. 2A is a graph showing X-ray diffraction analysis results of
the positive active materials according to Example 1 and
Comparative Example 1, and FIG. 2B is a graph enlarging a region
around a diffraction angle (2.theta.) of 19.degree. in FIG. 2A. In
addition, FIG. 3A is a graph showing X-ray diffraction analysis
results of the positive active materials according to Example 2 and
Reference Example 1, and FIG. 3B is a graph enlarging a region
around a diffraction angle (2.theta.) of 19.degree. in FIG. 3A.
Herein, "arb.unit", a unit in the vertical axis in FIGS. 2A, 2B,
3A, and 3B, indicates an arbitrary unit.
Referring to FIGS. 2A and 3A, the lithium nickel composite oxides
according to Examples 1 and 2, Comparative Example 1, and Reference
Example 1 showed a diffraction peak of a (003) phase at the
diffraction angle (2.theta.) of 19.degree. and a diffraction peak
(104) of a (104) phase at a diffraction angle (2.theta.) of
44.degree. in the X-ray diffraction analysis.
In addition, as shown in FIGS. 2B and 3B, Examples 1 and 2 (each
had a different oxygen partial pressure condition from that of
Comparative Example 1 and Reference Example 1 respectively) each
have a larger (e.g., greater) full width at half maximum
FWHM.sub.(003) of the diffraction peak of the (003) phase than
those of Comparative Example 1 and Reference Example 1
respectively, and thus the diffraction peak of the (003) phase was
extended.
In addition, the diffraction peak intensity ratio
I.sub.(003)/I.sub.(104) of the (003) phase and (104) phase, the
full width at half maximum (FWHM).sub.(003) of the diffraction peak
of the (003) phase, the full width at half maximum (FWHM).sub.(104)
of the diffraction peak of the (104) phase, and the average valence
of transition metals in the lithium nickel composite oxides
according to Examples 1 to 9, Comparative Examples 1 to 3, and
Reference Examples 1 to 3 were calculated based on a diffraction
peak of the X-ray diffractions of each of the examples and
comparative examples. The obtained results are provided in Table
3.
Herein, the average valence of transition metals was obtained by
measuring the oxygen amount of the lithium nickel composite oxide
with a carbon, hydrogen, nitrogen, sulfur/oxygen (CHNS/O) automated
elemental analyzer (2400II, PerkinElmer Inc.) and utilizing it as
described above.
Evaluation 2: Cycle Characteristics
Each lithium nickel composite oxide according to Examples 1 to 9,
Comparative Examples 1 to 3, and Reference Examples 1 to 3,
acetylene black, and polyvinylidene fluoride were mixed in a weight
ratio of 95:2:3, and then dispersed in N-methyl-2-pyrrolidone,
thereby preparing a slurry. The slurry was coated on an aluminum
foil and dried to form a positive active material layer, thus
manufacturing a positive electrode.
A negative electrode was manufactured by coating a metal lithium
foil on a copper foil.
A separator was manufactured as (manufactured utilizing) a 12
.mu.m-thick porous polyethylene film coated with a mixture of
Mg(OH).sub.2 particulates and polyvinylidene fluoride (PVdF) in a
weight ratio of 70:30.
The separator was disposed between the positive and negative
electrodes, thereby forming an electrode structure.
Subsequently, the electrode structure was processed to have a 2032
coin half-cell size and inserted into a coin half-cell container.
Then, an electrolyte solution was prepared by mixing ethylene
carbonate and dimethyl carbonate in a volume ratio of 3:7 to
prepare a non-aqueous solvent, and dissolving hexafluorolithium
phosphate (LiPF.sub.6) in a concentration of 1.3 mol/L therein.
Subsequently, the electrolyte solution was injected into the coin
half-cell container and impregnated into the separator, thereby
manufacturing a half-cell.
Charge and discharge cycle characteristics of rechargeable lithium
battery cells according to Examples 1 to 9, Comparative Examples 1
to 3, and Reference Examples 1 to 3 were evaluated, and the results
are provided in Table 3 and FIGS. 4A to 7.
For example, the cells were charged and discharged at a charge
rate, a discharge rate, and a cut-off voltage as provided in Table
2.
On the other hand, CC-CV in Table 2 indicates a constant
current/constant voltage charge, and CC indicates a constant
current discharge. The cut-off voltage indicates a voltage when the
charge and the discharge ended. For example, 4.3-3.0 under the
cut-off voltage indicates that the 1.sup.st cycle charge was
performed up to 4.3 V to which a voltage of a rechargeable lithium
battery cell was reached, and the 1.sup.st discharge was performed
down to 3.0 V to which a voltage of the rechargeable lithium
battery cell was reached.
TABLE-US-00002 TABLE 2 Test cycle Charge rate Discharge rate
Cut-off voltage [V] 1 0.2 C CC-CV 0.2 C CC 4.3-3.0 2 1.0 C CC-CV
1.0 C CC 4.3-3.0 3-49 1.0 C CC-CV 1.0 C CC 4.3-3.0 50 1.0 C CC-CV
1.0 C CC 4.3-3.0 51 0.2 C CC-CV 0.2 C CC 4.3-3.0
In Table 3, the "discharge capacity" indicates the discharge
capacity at the 2.sup.nd cycle; and the "cycle characteristics"
were evaluated by the capacity retention obtained by dividing the
discharge capacity at the 50th cycle by the discharge capacity at
the 2nd cycle, that is, a ratio of the discharge capacity at the
50th cycle relative to the discharge capacity at the 2nd cycle.
TABLE-US-00003 TABLE 3 Average particle Discharge Cycle diameter
Average capacity characteristics (.mu.m) FWHM.sub.(003)
FWHM.sub.(104) I.sub.(003)/I.sub.(104) valence (mA- h/g) (%)
Example 1 10 0.130 0.156 1.01 2.90 199 88 Example 2 10 0.140 0.167
0.93 2.94 203 86 Example 3 10 0.139 0.171 0.95 2.92 208 88 Example
4 10 0.131 0.178 0.97 2.92 212 88 Example 5 10 0.135 0.169 0.94
2.92 210 87 Example 6 10 0.145 0.172 0.97 2.92 198 88 Example 7 10
0.137 0.163 0.97 2.91 199 87 Example 8 10 0.142 0.170 0.95 2.93 196
88 Example 9 10 0.132 0.152 1.00 2.90 198 86 Comparative 10 0.128
0.145 1.03 2.86 198 77 Example 1 Reference 10 0.120 0.157 1.00 2.84
201 79 Example 1 Reference 10 0.152 0.206 0.94 2.95 174 86 Example
2 Reference 10 0.162 0.245 0.93 2.94 169 86 Example 3 Comparative
10 0.159 0.251 0.85 2.94 165 83 Example 2 Comparative 10 0.139
0.181 0.87 2.95 184 84 Example 3
Referring to Table 3, the cells according to Examples 1 to 9 had a
diffraction peak intensity ratio I.sub.(003)/I.sub.(104), a full
width at half maximum FWHM.sub.(003), a full width at half maximum
FWHM.sub.(104), and an average valence within each (e.g., their
respective) set or predetermined range according to one embodiment,
and thus showed high discharge capacity and excellent cycle
characteristics.
On the other hand, the cells according to Comparative Example 1 and
Reference Example 1 had a full width at half maximum FWHM.sub.(003)
and an average valence beyond the range of one embodiment (e.g.,
outside of their respective range according to one embodiment) and
thus showed deteriorated cycle characteristics. In addition, the
cells according to Reference Examples 2 and 3, and Comparative
Example 2 had a full width at half maximum FWHM.sub.(003) and a
full width at half maximum FWHM.sub.(104) beyond (e.g., outside)
the range of one embodiment and thus showed deteriorated discharge
capacity. Furthermore, the cell of Comparative Example 3 had a full
width at half maximum FWHM.sub.(104) and a diffraction peak
intensity ratio I.sub.(003)/I.sub.(104) beyond (e.g., outside) the
ranges of one embodiment and thus showed deteriorated discharge
capacity.
In addition, the result of Table 3 was scatter-plotted in FIGS. 4A
to 5B.
FIG. 4A is a graph showing the discharge capacities regarding
(versus) the full width at half maximum FWHM.sub.(003) of the
positive active materials according to Examples 1 to 9, Comparative
Examples 1 to 3, and Reference Examples 1 to 3, and FIG. 4B is a
graph showing the cycle characteristics regarding (versus) the full
width at half maximum FWHM.sub.(003) of the positive active
materials according to Examples 1 to 9, Comparative Examples 1 to
3, and Reference Examples 1 to 3. In addition, FIG. 5A is a graph
showing the discharge capacities regarding (versus) the full width
at half maximum FWHM.sub.(104) of the positive active materials
according to Examples 1 to 9, Comparative Examples 1 to 3, and
Reference Examples 1 to 3, and FIG. 5B is a graph showing the cycle
characteristics regarding (versus) the full width at half maximum
FWHM.sub.(104) of the positive active materials according to
Examples 1 to 9, Comparative Examples 1 to 3, and Reference
Examples 1 to 3.
In FIG. 4A to FIG. 5B, a "circled" dot indicates the examples, and
a number assigned to them indicates the number of the examples. In
addition, a "rhombic" dot indicates the comparative examples, and a
number assigned to them indicates the number of the comparative
examples.
Referring to FIGS. 4A and 4B, Comparative Example 1 and Reference
Example 1 having a smaller full width at half maximum
FWHM.sub.(003) than the range of one embodiment showed deteriorated
cycle characteristics, while Reference Examples 2 and 3,
Comparative Example 2 having a larger full width at half maximum
FWHM.sub.(003) than the range of one embodiment showed deteriorated
discharge capacity.
On the other hand, Examples 1 to 9 having a full width at half
maximum FWHM.sub.(003) within the range of one embodiment
maintained the discharge capacity and showed improved cycle
characteristics.
Comparative Example 3 had a full width at half maximum
FWHM.sub.(003) within the range of one embodiment but a full width
at half maximum FWHM.sub.(104) out of the range of one embodiment,
and thus showed deteriorated discharge capacity and cycle
characteristics.
In addition, referring to FIGS. 5A and 5B, Comparative Example 1
having a smaller full width at half maximum FWHM.sub.(104) than the
range of one embodiment showed deteriorated cycle characteristics,
but Reference Examples 2 and 3, and Comparative Examples 2 and 3
having a larger full width at half maximum FWHM.sub.(104) than the
range of one embodiment showed deteriorated discharge capacity.
On the other hand, Examples 1 to 9 had a full width at half maximum
FWHM.sub.(104) within the range of one embodiment and thus
maintained the discharge capacity and showed improved cycle
characteristics.
Reference Example 1 had a full width at half maximum FWHM.sub.(104)
within the range of one embodiment but a full width at half maximum
FWHM.sub.(003) out of the range of one embodiment and showed
deteriorated cycle characteristics.
In addition, FIGS. 6 and 7 are graphs plotting changes in the
discharge capacity of Examples 1 and 2, Comparative Example 1, and
Reference Example 1 depending on a charge and discharge cycle.
FIG. 6 is a graph showing the change in the discharge capacity of
the rechargeable lithium battery cells according to Example 1 and
Comparative Example 1 depending on a charge and discharge cycle (as
a function of the number of charge and discharge cycles), and FIG.
7 is a graph showing a change in the discharge capacity of the
rechargeable lithium battery cells according to Example 2 and
Reference Example 1 depending on a charge and discharge cycle.
Referring to FIG. 6, the cell utilizing a lithium nickel composite
oxide fired under a high oxygen partial pressure according to
Example 1 maintained the high discharge capacity despite the
repeated charge and discharge cycles compared with the cell
according to Comparative Example 1.
In addition, referring to FIG. 7, the cell utilizing a lithium
nickel composite oxide fired under an oxygen partial pressure
according to Example 2 maintained the high discharge capacity
despite the repeated charge and discharge cycles compared with the
cell according to Reference Example 1.
Accordingly, the lithium nickel composite oxides according to the
examples had a diffraction peak intensity ratio
I.sub.(003)/I.sub.(104), a full width at half maximum
FWHM.sub.(003), a full width at half maximum FWHM.sub.(104), and an
average valence of transition metals within the ranges of one
embodiment in the X-ray diffraction, and had improved cycle
characteristics of lithium rechargeable battery cells.
Evaluation 3: Rate Capability
Each lithium nickel composite oxide according to Examples 1 and 2
and Comparative Examples 1 and 2, acetylene black, and
polyvinylidene fluoride were mixed in a weight ratio of 95:2:3 and
dispersed in N-methyl-2-pyrrolidone, thereby preparing a slurry.
The slurry was coated on an aluminum foil and dried to form a
positive active material layer, thus manufacturing a positive
electrode.
A negative electrode was manufactured by coating a metal lithium
film on a copper foil.
As for a separator, a 12 .mu.m-thick porous polypropylene film was
utilized.
The separator was disposed between the positive and negative
electrodes, thereby forming an electrode structure.
Subsequently, the electrode structure was processed into a 2032
coin half-cell size and inserted into a coin half-cell container.
Then, an electrolyte solution was prepared by mixing ethylene
carbonate and dimethyl carbonate in a volume ratio of 3:7 to
prepare a non-aqueous solvent, and dissolving hexafluorolithium
phosphate (LiPF.sub.6) in a concentration of 1.3 mol/L therein.
Subsequently, the electrolyte solution was injected into the coin
half-cell container and impregnated into the separator, thereby
manufacturing a half-cell.
Rate capability of the rechargeable lithium battery cells according
to Examples 1 and 2, Comparative Example 1, and Reference Example 1
was evaluated, and the results are provided in FIGS. 8 to 11.
For example, the cells were charged and discharged at a charge
rate, a discharge rate. and a cut-off voltage as provided in Table
4.
On the other hand, in Table 4, CC-CV indicates a constant
current/constant voltage charge, and CC indicates a constant
current discharge. A cut-off voltage indicates a voltage when
charge and discharge ended. For example, 4.3-2.8 under the column
of Cut-off voltage indicates that a charge at the 1st cycle was
performed up to 4.3 V to which a voltage of the rechargeable
lithium battery was reached, and a discharge at the 1st cycle was
performed down to 2.8 V to which a voltage of the rechargeable
lithium battery was reached.
TABLE-US-00004 TABLE 4 Test cycle Charge rate Discharge rate
Cut-off voltage [V] 1 0.1 C CC-CV 0.1 C CC 4.3-2.8 2 0.2 C CC-CV
0.2 C CC 4.3-2.8 3 0.2 C CC-CV 1.0 C CC 4.3-2.8 4 0.2 C CC-CV 2.0 C
CC 4.3-2.8 5 0.2 C CC-CV 3.0 C CC 4.3-2.8 6 0.2 C CC-CV 5.0 C CC
4.3-2.8
FIG. 8 is a graph showing the 1.sup.st cycle charge and discharge
curves of the rechargeable lithium battery cells according to
Example 1 and Comparative Example 1, and FIG. 9 is a graph showing
the 1.sup.st cycle charge and discharge curves of the rechargeable
lithium battery cells according to Example 2 and Reference Example
1.
Referring to FIG. 8, the cell of Example 1 was suppressed from
having a voltage increase at the initial charge compared with the
cell of Comparative Example 1 when charged at a charge rate of 0.1
C CC-CV and discharged at a discharge rate of 0.1 C CC for one
cycle.
In addition, each charge capacity at a 0.1 C charge, discharge
capacity at a 0.1 C discharge, and initial efficiency of Example 1
and Comparative Example 1 were measured, and the results are
provided in Table 5.
On the other hand, initial efficiency was calculated by dividing
the discharge capacity at a 0.1 C discharge by the charge capacity
at a 0.1 C charge.
TABLE-US-00005 TABLE 5 Charge capacity Discharge capacity Initial
at 0.1 C charge at 0.1 C discharge efficiency [mAh/g] [mAh/g] [%]
Example 1 229 204 89.1 Comparative 230 202 87.6 Example 1
Referring to Table 5, the cell utilizing a lithium nickel composite
oxide fired under a high oxygen partial pressure according to
Example 1 showed increased discharge capacity at the 0.1 C
discharge compared with the cell of Comparative Example 1, and thus
showed an increased initial efficiency.
In addition, referring to FIG. 9, when Example 2 and Reference
Example 1 were charged at a charge rate of 0.1 C CC-CV and
discharged at a discharge rate of 0.1 C CC, Example 2 was
suppressed from having a voltage increase at the initial charge
compared with Reference Example 1.
Charge capacity at the 0.1 C charge, discharge capacity at the 0.1
C discharge, and the initial efficiency of Example 2 and
Comparative Example 2 were measured, and the results are provided
in Table 6.
TABLE-US-00006 TABLE 6 Charge capacity Discharge capacity Initial
at 0.1 C charging at 0.1 C discharging efficiency [mAh/g] [mAh/g]
[%] Example 2 233 208 89.3 Reference 232 206 88.5 Example 1
Referring to Table 6, the cell utilizing a lithium nickel composite
oxide fired under a high oxygen partial pressure according to
Example 2 showed increased discharge capacity at the 0.1 C
discharge and thus increased initial efficiency compared with the
cell of Reference Example 1.
In addition, referring to FIGS. 10 and 11, the discharge capacity
at each discharge rate is illustrated.
FIG. 10 is a graph showing the discharge capacity of the
rechargeable lithium battery cells according to Example 1 and
Comparative Example 1 at each discharge rate, and FIG. 11 is a
graph showing the discharge capacity of the rechargeable lithium
battery cells of Example 2 and Reference Example 1 at each
discharge rate.
Referring to FIG. 10, Example 1 utilizing the lithium nickel
composite oxide fired under a high oxygen partial pressure showed
equivalent or higher discharge capacity than Comparative Example 1
at each discharge rate. For example, Example 1 had a ratio
(obtained by dividing the discharge capacity at a discharge rate of
3.0 C by the discharge capacity at a discharge rate of 0.33 C) of
91.9%, while Comparative Example 1 had a ratio of 91.8%.
Accordingly, Example 1 had almost an equivalent rate capability
compared with Comparative Example 1.
Likewise, referring to FIG. 11, Example 2 utilizing lithium nickel
composite oxide fired under a high oxygen partial pressure showed
an equivalent or higher discharge capacity than Reference Example 1
at each discharge rate. For example, Example 2 had a ratio
(obtained by dividing the discharge capacity at a discharge rate of
3.0 C by the discharge capacity at a discharge rate of 0.33 C) of
91.3%, while Reference Example 1 had a ratio of 90.7%. Accordingly,
Example 2 had an almost equivalent rate capability to Reference
Example 1.
Based on the above results, when a rechargeable lithium battery
cell according to one embodiment utilized the lithium nickel
composite oxide fired under a high oxygen partial pressure, having
a diffraction peak intensity ratio I.sub.(003)/I.sub.(104) of
greater than or equal to 0.92 to less than or equal to 1.02, a full
width at half maximum FWHM.sub.(003) of greater than or equal to
0.13 to less than or equal to 0.15, a full width at half maximum
FWHM.sub.(104) of greater than or equal to 0.15 to less than or
equal to 0.18, and an average valence of the transition metal of
2.9 in the X-ray diffraction as a positive active material, the
rechargeable lithium battery cell showed improved cycle
characteristics.
In addition, referring to Table 3, a rechargeable lithium battery
cell according to one embodiment did not exhibit deteriorated
discharge capacity but did exhibit improved cycle
characteristics.
Furthermore, referring to the results of FIGS. 8 to 11, the
rechargeable lithium battery cell according to one embodiment
showed improved cycle characteristics without deterioration of
other characteristics (such as the initial charge and discharge
characteristics, rate capability, and/or the like).
According to one embodiment, cycle characteristics of a
rechargeable lithium battery cell may be improved by improving the
stability of a lithium nickel composite oxide including Ni at a
ratio greater than or equal to 55%, for example, greater than or
equal to 80%.
While this disclosure has been described in connection with what is
presently considered to be practical exemplary embodiments, it is
to be understood that the invention is not limited to the disclosed
embodiments, but, on the contrary, is intended to cover various
modifications and equivalent arrangements included within the
spirit and scope of the appended claims, and equivalents
thereof.
DESCRIPTION OF SYMBOLS
10 rechargeable lithium battery 20 positive electrode 21 current
collector 22 positive active material layer 30 negative electrode
31 current collector 32 negative active material layer 40 separator
layer
* * * * *